The present invention relates to a profiled pneumatic vehicle tire having a tread surface that includes grooves that, when viewed in plan extend at an angle relative to the circumferential direction or direction of operation of the tire, with the grooves having sides that extend at an angle relative to a radial line, and with the distance between successive angled grooves in the circumferential direction being modulated in conformity with a design cycle or pitch sequence that varies the excitation frequency, so that positive profiling portions having varying dimensions in the circumferential direction are provided between the inclined groove, with the dimension of the grooves in the circumferential direction being also modulated in conformity with the pitch sequence for the distance between successive grooves.
A tire of this general type is disclosed in U.S. Pat. No. 4,327,792, Landers, which defines the terminology that is also employed in the instant application.
With such pneumatic vehicle tires, the sides of the grooves are angled relative to radial lines in such a way that the grooves widen in a radially outward direction. Such a configuration is intended in particular to enhance the discharge of stones and the like, i.e. the self cleaning effect of the profiling. The angle of inclination of the groove sides is customarily approximately between 5.degree. to 30.degree.. This angular configuration of the groove sides also facilitates the removal of such tires from the vulcanization presses. Up to now, the angling of the sides has been kept as small as possible yet large enough to meet application requirements and the respective tread surface mixture. The angle of the sides has sometimes been varied in the axial direction, but has never been varied in the circumferential direction.
Heretofore known tires of this type have the drawback that their resistance to skidding fluctuates over the periphery. This results in irregular longitudinal and transverse accelerations.
Due to rising demands to lower the noise level, the use of a pitch sequence that varies the excitation frequency cannot be avoided in modern pneumatic vehicle tires, regardless of whether passenger car or truck tires are involved. Unfortunately, with tires constructed in this manner the effect is observed that the effectiveness of the pitch sequence deteriorates over the lifetime of the tire as wear occurs. In this connection, the amplitude of the low frequency vibrations, in other words the vibrations below the so-called block harmonic, increases relative to the higher frequency vibrations. The block harmonic is the product of the rotational frequency of the tire (essentially a function of vehicle speed and contact circumference) times the number of profiled blocks in the circumferential direction.
The present invention relates in particular to large-block tires for trucks and cross-country vehicles, where both of the aforementioned problems, and in particular irregular traction, are particularly problematic.
It is an object of the present invention, while maintaining the resonance-varying pitch sequence for the pneumatic vehicle tire profiling, to mitigate the aforementioned drawbacks.